Hornady OAL gauge ????

Discussion in 'Reloading' started by bigbuck, Dec 28, 2009.

  1. bigbuck

    bigbuck Well-Known Member

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    I went to SW over the wekend and picked up a Hornady OAL gauge they did not have a Remington 300 RUM dummy round in stock so when I got home I was reading the instructions that came with it and they said to send 2 pcs of fired brass to them and they could tap and thread it to fit the OAL gauge my question is have any of you guys tapped it yourself if so could you tell me what size tapp that I would need to pick up ? Thanks in advance.

    Bigbuck
     
  2. boomtube

    boomtube Well-Known Member

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    It can be done but the thread specs are not common or easily available. Forget what it is but having Hornady do it would probably be cheeper than buying the tap.

    Since the threads COULD just as easily be conventional I suspect they do that odd size to trap us into buying the silly things from them. I quite using it, went back to the old method of a marked (dowel) rod. It's just as accurate as the Hornady tool, actually easier to do and a dowel costs less than a buck.

    I do use the "case headspace" tool tho, it works well.
     

  3. bigbuck

    bigbuck Well-Known Member

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    I also bought the hornady comperator I believe that's what it's called? I hope I didn't blow $34.00 on the stoney point gauge.....

    Bigbuck
     
  4. MTBULLET

    MTBULLET Well-Known Member

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    tap is 5/16-36, easily done ,
    (especiall in a lathe with collet chuck) and if you own the tap, you can make any size case you need. This pays for the tap in short order.
     
  5. bigbuck

    bigbuck Well-Known Member

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    Thanks just what I was looking for:)

    Bigbuck
     
  6. Varmint Hunter

    Varmint Hunter Well-Known Member

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    I've had the cases from several wildcat cartridges tapped by Stoney Point when they originally designed and produced the tool. It is cheaper to just buy the modified cases from a mailorder house than it is to have Hornady tap one for you.

    Midsouth Shooters Supply or Midway USA would be good places to look.
     
  7. bigbuck

    bigbuck Well-Known Member

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    I believe that the instructions said to send $11.00 to hornady and they would do it. I think it also mentioned that the case from my rifle would be better since it was fire formed from my exact chamber. What is your thoughts on this?
     
  8. jmason

    jmason Well-Known Member

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    I don't see how that would make any difference to the measurement your trying to obtain with the tool.
     
  9. bigbuck

    bigbuck Well-Known Member

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    You have a very good point. I may have misread the directions of course I would never do that:rolleyes: I would rather just order their case and be done with it but if it would be any better then I would just use mine. Sometimes the more I try to learn the more problems it causes LOL

    Bigbuck
     
  10. woods

    woods Well-Known Member

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    There would be a difference in the measurement between using the modified case and a fire formed case. For the 300 RUM, since it is an unbelted case, to take the measurement with a Hornady modified case, you insert it into the chamber and seat if firmly as far forward as possible. That means the case head will be in a different position than a fire formed case held in stasis between the bolt face and shoulder.

    Think of it this way; if you measured the Hornady modified case and the fire formed case with a HEADSPACE Gauge, those measurements will be different. IOW the measurement from the case head to the datum line
    [​IMG]

    will be shorter on the Hornady modified case than on the fire formed chamber sized case.

    But you also have to consider that if you use the same OAL measurement to seat bullets in new cases as you do on fire formed cases, then the distance to the lands will be different. Consider that when you chamber a new case that is loaded to an OAL of 3.625" (to fit the mag of the typical long throated 300RUM), that new case will be pushed forward before firing by the ejector button in the chamber and when the primer fires it will be pushed forward by the amount of headspace you have, THUS SHORTENING THE DISTANCE TO THE LANDS.

    For example, and I know this is tedious but there is no easy way to explain it, on a 300RUM that I reload for (factory Sendero) the measurement from the case head to the datum line as measured by a Hornady Headspace Gauge (Remington brass) is 2.463". The same measurement on a 3 times fired fully expanded case is 2.473", which means the gun has a headspace of .010" with that particular brass. The brass will be moved forward in the chamber that distance of .010" either by the ejector button or the primer firing and if you were seating .010" off the lands, you would now be seated ON THE LANDS.

    So you need to take all this into account and you can only be sure of one thing, your distance to the lands will only be correct if you take the measurements on fully fire formed brass or you allow for the headspace on new ones.

    But in all likelihood you will not need the OAL gauge anyway with a 300RUM because all that I have seen have been long throated and you have to seat to fit the mag anyway. Which on the 2 that I reload for when seated at a fit-the-mag-length of 3.625" is .160" off the lands on the factory Sendero and .165" off the lands in a custom Bansner Sheep Rifle.
     
  11. bigbuck

    bigbuck Well-Known Member

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    Thanks for the post it is very helpful I also load so that i'm just clearing the factory Mag, but I failed to mention that I just bought a wyatts extended box from midway so when hunting season is over I'm going to attempt to install it myself ,then I hope to get the full benefit of the OAL gauge I shoot the 210 bergers so I'm hoping to get better accuracey as well. Seems like i've read in other posts that they are jumping the bergers .010 off the lands .

    Bigbuck
     
  12. Chief1942

    Chief1942 Well-Known Member

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    Uh, yeah. What he said.:D